Study On Volatile And Characteristic Aroma Components Among Essential Oil And Aqueous Effluents From Cold-Pressing Process Of Orange Peel Oil

Sweet orange essential oil is one of the most important products in citrus deep processing field.It is abundant in the oil cells of the peel of sweet orange and has a pleasant and unique aromatic flavor.The aroma is derived from the volatile substances contained in it,mainly composed of terpenes,alcohols,aldehydes and esters.In addition,sweet orange oil also has anti-cancer,antibacterial,antioxidant,anti-inflammatory and antiviral effects,so it is widely used in cosmetics and pharmaceutical industries.Chongqing is the major sweet orange planting and processing province in China,there are 4-5 large-scale citrus processing enterprises with relatively complete processing system..Cold pressing is the main method to produce high quality sweet orange essential oil,which has great commercial value.The essential oil obtained by this mothod most close to its natural composition,and its aroma quality is closer to that of fresh fruit.In order to meet the needs of industrial development and technological upgrading,this paper studies the volatile of cold-pressed oil from late-maturing sweet oranges,and further analysis the volatiles and principal aroma components differences among aqueous effluents and essential oil.In order to rich the essential oil resources and provide a scientific advice for enhancing the added value of late-maturing sweet orange products.The main research contents and results of are as follows:(1)Volatile organic compounds(VOCs)contained in three varieties of sweet orange CPO were qualitatively and quantitatively analyzed by headspace solid-phase micro-extraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS)combined with retention index(RI).The results showed that 64,67 and 65 volatile components were identified in Olinda,Wu Yue Hong and Blood orange CPO respectively,the total concentration of volatile compounds in three CPO was 56403.84 ?g/m L,62734.20 ?g/m L and 55450.04?g/m L,respectively,they were mainly composed of monoterpenes,alcohols and aldehydes,with the advantage of low D-limonene content(?86% m/m);Olinda CPO contained higher concentrations of alcohols,Wu Yue Hong and Tarocco blood orange CPO contained higher concentrations of monoterpenes and Carbonyl(aldehydes and ketones)volatile compounds,respectively.(2)By calculating the odor activity values(OAV),the main aroma components of different CPO were compared,and it was found that the types of main aroma contributing components of the three varieties of CPO were similar,there were 19 main aroma components including p-cymene,octanal,hexanal,nonanal and linalool,et al;The total OAV of each aroma attribute was further calculated,and it was found that there was a significant difference(p<0.01)in the proportion of the total OVA of each aroma attribute among three kinds of CPO.which mainly characterized by citrusy and fatty notes,the total OAV of piney and floral aroma attribute was the highest in Olinda CPO,while the total OAV of green aroma attributes was the highest in Tarocco blood orange CPO.(3)Oil-water separation is the key step of producing citrus peel essential oil by cold pressing methods.The aqueous effluents(AEs)and cold-pressed oil of Valencia Orange were qualitatively and quantitatively analyzed respectively for their VOCs,the results showed that 75,72 and 63 VOCs were identified respectively in AE I,AEII and CPO samples(77 in total).Eleven components with high water solubility were only identified in AEs,including ethanol,(Z)-2-penten-1-ol,ethyl acetate,2,3-butanedione and(E)-2-pentenal,but absent from the CPO.Concentration of most VOCs in CPO is30?50 times higher than that of AE I.However,considered the respective volume of the three samples,the total VOCs content in AE I was much higher than CPO's.(4)The differences of characteristic volatile components and aroma properties between oil and AEs were analyzed by gas-chromatography-olfactometry(GC-O)and sensory evaluation.GC-O test results showed that a total of 16 aromatic substances were detected,including 6 aldehydes,7 terpenoids,1 alcohol and 2 uncertain components.The component with high sniffing intensity in three samples were?-Myrcene,D-limonene,octanal,linalool,decanal and others.Sensory evaluation showed that there was a significant difference(P?0.05)in same attributes of different samples(except piney),AEI was strong in floral but weak in citrusy,AE II was strong in fatty and piney,but weak in floral,CPO's grassy and citrusy had prominent sensory attributes and the highest score,while its fatty was weaker than AE I and AE II.The flavor profile was obtained through GC-O result,and compared it with the sensory evaluation results,found that there was a good correspondence in grassy,floral and fatty attributes.(5)OAV study and recombination experiment were carried out of CPO,AE I and AE II.The results showed that a total of 25 volatile substances' OAV was ?1,among which the OAV of aldehydes such as octanal,nonanal and decanal were above the average level.Combined with the GC-O results,14 most important aromatic characteristic compounds were finally screened out,including hexanal,?-pinene,?-myrcene,?-terpene,D-limonene,nonanal,p-cymene,terpenone,octanal,linalool,citronellal,decanal,nerval and valencene.Recombination experiment results show that the overall sensory profile of the reconstituted sample is closer to that of the original sample.